Auto merge of #117722 - okaneco:binarysearch, r=thomcc

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Refactor `binary_search_by` to use conditional moves

Refactor the if/else checking on `cmp::Ordering` variants to a "branchless" reassignment of left and right.

This change results in fewer branches and instructions.
https://rust.godbolt.org/z/698eYffTx

---

I saw consistent benchmark improvements locally. Performance of worst case seems about the same, maybe slightly faster for the L3 test.

Current
```
slice::binary_search_l1             43.00ns/iter +/- 3.00ns
slice::binary_search_l1_with_dups   25.00ns/iter +/- 0.00ns
slice::binary_search_l1_worst_case  10.00ns/iter +/- 0.00ns
slice::binary_search_l2             64.00ns/iter +/- 1.00ns
slice::binary_search_l2_with_dups   42.00ns/iter +/- 0.00ns
slice::binary_search_l2_worst_case  16.00ns/iter +/- 0.00ns
slice::binary_search_l3            132.00ns/iter +/- 2.00ns
slice::binary_search_l3_with_dups  108.00ns/iter +/- 2.00ns
slice::binary_search_l3_worst_case  33.00ns/iter +/- 3.00ns
```
This PR
```
slice::binary_search_l1            21.00ns/iter +/- 0.00ns
slice::binary_search_l1_with_dups  14.00ns/iter +/- 0.00ns
slice::binary_search_l1_worst_case  9.00ns/iter +/- 0.00ns
slice::binary_search_l2            34.00ns/iter +/- 0.00ns
slice::binary_search_l2_with_dups  23.00ns/iter +/- 0.00ns
slice::binary_search_l2_worst_case 16.00ns/iter +/- 0.00ns
slice::binary_search_l3            92.00ns/iter +/- 3.00ns
slice::binary_search_l3_with_dups  63.00ns/iter +/- 1.00ns
slice::binary_search_l3_worst_case 29.00ns/iter +/- 0.00ns
```

...

This commit is contained in:

bors 2023-11-24 07:23:04 +00:00

parent 46fb59c59e 30b7c1400f

commit 85fd36d48d

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

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